[PATCH] PATCH: 1 line 2.6.18 bugfix: modpost-64bit-fix.patch

There is a small but annoying bug in scripts/mod/file2alias.c which causes
it to generate invalid aliases for input devices on 64 bit archs. This causes
joydev.ko to not be automaticly loaded when inserting a joystick, resulting in
a non working joystick (for the average user).

In scripts/mod/file2alias.c is the following code for generating the input
aliases:
static void do_input(char *alias,
                     kernel_ulong_t *arr, unsigned int min, unsigned int max)
{
        unsigned int i;

        for (i = min; i < max; i++)
                if (arr[i / BITS_PER_LONG] & (1 << (i%BITS_PER_LONG)))
                        sprintf(alias + strlen(alias), "%X,*", i);
}

On 32 bits systems, this correctly generates "0,*" for the first alias, "8,*"
for the second etc.

However on 64 bits it generates: "0,*20,*" resp "8,*28,*" Notice how it adds 20
+ first entry (hex) ! to the list of hex codes, which is 32 more then the first
entry, thus is because the bit test above wraps at 32 bits instead of 64.

scripts/mod/file2alias.c, line 379 reads:
                if (arr[i / BITS_PER_LONG] & (1 << (i%BITS_PER_LONG)))
That should be:
                if (arr[i / BITS_PER_LONG] & (1L << (i%BITS_PER_LONG)))

Notice the added 'L' after the 1, otherwise that is an 32 bit int instead of a
64 bit long, and when that int gets shifted >= 32 times, appearantly the number
by which to shift is wrapped at 5 bits ( % 32) causing it to test a bit 32 bits
too low.

The patch below makes the nescesarry 1 char change :)

Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 4431292..e2de650 100644 (file)
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -391,7 +391,7 @@ static void do_input(char *alias,
        unsigned int i;
 
        for (i = min; i < max; i++)
-               if (arr[i / BITS_PER_LONG] & (1 << (i%BITS_PER_LONG)))
+               if (arr[i / BITS_PER_LONG] & (1L << (i%BITS_PER_LONG)))
                        sprintf(alias + strlen(alias), "%X,*", i);
 }